Current Storage Area Networks (SANs) are designed to carry block storage traffic over predominantly Fibre Channel standard medium and protocols using fabric networks comprising local area networks (LANs). Expansion of SAN fabric networks is limited in that conventional SAN fabric channels cannot be implemented over geographically distant locations. Conventional Fibre Channel architecture is not suitable for WAN/LAN applications. While SCSI and Ethernet may be used to implement a WAN/LAN, these two protocols are not efficient for storage applications. Accordingly, current SAN fabric networks are limited to a single geographic location.
There exist several proposals for moving block storage traffic over SANs built on other networking medium and protocol technologies such as Gigabit Ethernet, ATM/SONET, Infiniband, and the like. Presently, to bridge or interconnect storage data traffic from SANs using one medium/protocol type to another SAN using an incompatible protocol/medium type requires devices and software that perform the necessary protocol/medium translations. These translation devices, hereinafter referred to as “translation bridges,” make the necessary translations between incompatible protocol/mediums in order to serve the host computers/servers and storage target devices (the “clients”). Interconnecting heterogeneous SANs that may be easily scaled upward using these translation bridges is very difficult because the translation bridges usually become the bottleneck in speed of data transfer when the clients (servers and/or storage devices) become larger in number. In addition, in a mixed protocol environment and when the number of different protocols increase, the complexity of the software installed on the translation bridges increases, which further impacts performance.
A limitation of the size of SAN fabric networks, in terms of storage capacity, is cost and manpower. In order to expand the storage capacity of a SAN fabric network, storage devices such as disk drives, controllers, fiber channel switches and hubs, and other hardware must be purchased, interconnected and made functionally operable together. Another major, if not primary, expense is the cost of managing a SAN. SAN management requires a lot of manpower for maintenance and planning. For example, as storage capacity grows, issues such as determining server access to storage devices, backup strategy, data replication, data recovery, and other considerations become more complex.
It is desirable that next generation storage network switch systems will have ingress and egress ports that support different protocols and network media so that different types of host computer/servers and storage target devices may be attached directly to the switch system and start communicating with each other without translation overhead. In order to communicate between any two ports, the source and destination ports must be identifiable in both the source and destination protocol. For example, to send a message or frame from a Fibre Channel port to a Gigabit Ethernet port, the destination port needs to appear as a Fibre Channel port to the connected Fibre Channel source, and the source port needs to appear as a Gigabit Ethernet port to the destination port.
Storage Area Network (SAN) and networking products are usually used in mission critical applications and housed in chassis or racks. When a customer wants to expand this system, one or more chassis are added into the existing domain. However, the user has to power down the existing system and reconnect the new chassis into the existing system. Once the new configuration or topology is complete, the user will have to power on the new system. Unfortunately, this upgrade causes system downtime and potentially loss of revenue.
Switches have a limited resource—the switch fabric or routing core. A non-blocking switch must have enough bandwidth to receive traffic at full speed from all ingress ports and direct the traffic to the egress ports without dropping traffic, assuming that the traffic is spread equally across all egress ports and does not congest one of them. Therefore, if all ports connected to the switch have the same data rate, then the switch fabric must have bandwidth greater than the number of ports multiplied by the port speed if it wants to be a non-blocking switch that does not drop traffic.
The problem with existing switches is that the internal switch fabric is fixed in size. If large scalability is desired one has to pay for a large switch fabric that initially is not needed. In present systems a smaller switch has to be replaced when more capacity is needed by a larger switch. This is a disruptive upgrade that causes all nodes connected to the switch to loose connectivity while the upgrade is occurring. In another scenario, multiple smaller switches can be interconnected using lower bandwidth interconnects. However, these interconnects can become congested and limit the throughput of the network.
The majority of the SAN switches are not expandable and typically have a limited number of ports, for example, 16 ports. When a customer needs more than 16 ports two or more of the 16 port switches must be connected together. Unfortunately, to achieve a non-blocking switch in a typical configuration half of the ports on the switch are then used for interconnect purposes.
Some larger switches are based on a chassis design where cards plug into a backplane. This design allows the user to add and remove ports. However, switches are typically designed with a fixed amount of switching bandwidth. The cost of this bandwidth must be amortized over each port. Therefore, if you purchase a switch with large growth potential but start with a modest number of ports you have a higher initial investment than necessary. Also, when a customer fills up the chassis the system still has the problem of expansion. If a chassis supports non-blocking expansion, then it normally has to have twice the required bandwidth.
Furthermore, to expand a system according to the prior art, the system usually has to be shut down. Depending on the design of the system, there might be a significant time gap between the shutdown and the power up of the expanded system due to reconfiguration time and manual labor that has to be performed. This will cause significant loss of revenue during down time.
Thus, there is a demand for a more user friendly system reducing the downtime and overall cost of a network switch fabric system.